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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 230 · 40 questions
TalentJR

Developer's tip (When this, do that): Event → handler → action: “on tap, do this”. The handler runs once for every tap. Counter: start + taps × step. A limit stops it growing; on = !on flips ON / OFF.

NameDateTime takenScore ___ / 40
  1. 1.👆 The user taps the button 4 times. What number does the label show now?
    let score = 5;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  2. 2.👆 What kind of event is this: one second passes? (a) a timer event (b) a text event (c) a load event (d) a tap event
  3. 3.True or false: a 5-minute alarm ends is a text event. (a) True (b) False
  4. 4.True or false: the user taps Play is a tap event. (a) False (b) True
  5. 5.👆 “On tap → do this” links an event to ___. (a) an action (b) a web address (c) a font (d) a charger
  6. 6.👆 An event in an app is ___. (a) a colour theme (b) something that happens (c) an app store (d) a kind of list
  7. 7.👆 The user taps the button 6 times. What number does the label show now?
    let lives = 0;
    button.onTap = function () {
      lives = lives + 4;
      label.text = lives;
    };
  8. 8.👆 The user taps the button 6 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  9. 9.👆 What kind of event is this: a 5-minute alarm ends? (a) a load event (b) a text event (c) a timer event (d) a tap event
  10. 10.👆 What kind of event is this: the app starts up? (a) a load event (b) a timer event (c) a text event (d) a tap event
  11. 11.👆 The user taps the button 2 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    };     (a) ON (b) OFF
  12. 12.👆 The user types Riya in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hi, " + nameBox.text + "!";
    };     (a) Hi! (b) Hi, Riya! (c) Riya (d) Hi, nameBox.text!
  13. 13.👆 What kind of event is this: a finger hits Like? (a) a text event (b) a timer event (c) a tap event (d) a load event
  14. 14.👆 Which of these is an event? (a) the icon colour (b) the user taps a button (c) a list of names (d) the font size
  15. 15.👆 The user taps the button 7 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    };     (a) OFF (b) ON
  16. 16.👆 The user types Kabir in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Kabir (b) Hello! (c) Hello, nameBox.text! (d) Hello, Kabir!
  17. 17.👆 The user types Zoya in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Hello! (b) Zoya (c) Hello, nameBox.text! (d) Hello, Zoya!
  18. 18.👆 What kind of event is this: the user presses Save? (a) a tap event (b) a text event (c) a load event (d) a timer event
  19. 19.👆 The user taps the button 4 times. What number does the label show now?
    let score = 7;
    button.onTap = function () {
      score = score + 4;
      label.text = score;
    };
  20. 20.👆 The user types Kabir in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hi, " + nameBox.text + "!";
    };     (a) Hi, Kabir! (b) Kabir (c) Hi! (d) Hi, nameBox.text!
  21. 21.👆 The user taps the button 6 times. What number does the label show now?
    let coins = 1;
    button.onTap = function () {
      coins = coins + 3;
      label.text = coins;
    };
  22. 22.👆 The user taps the button 6 times. What number does the label show now?
    let points = 9;
    button.onTap = function () {
      points = points + 3;
      label.text = points;
    };
  23. 23.True or false: the search box changes is a tap event. (a) False (b) True
  24. 24.True or false: a 5-minute alarm ends is a timer event. (a) False (b) True
  25. 25.👆 The user types Aman in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Well done, " + nameBox.text + "!";
    };     (a) Well done, Aman! (b) Well done, nameBox.text! (c) Aman (d) Well done!
  26. 26.True or false: a countdown hits zero is a load event. (a) True (b) False
  27. 27.👆 What kind of event is this: the user types a letter? (a) a tap event (b) a load event (c) a timer event (d) a text event
  28. 28.👆 The user taps the button 3 times. What number does the label show now?
    let stars = 1;
    button.onTap = function () {
      stars = stars + 1;
      label.text = stars;
    };
  29. 29.👆 The user types Aman in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Hello, nameBox.text! (b) Hello! (c) Hello, Aman! (d) Aman
  30. 30.👆 The user taps the button 7 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  31. 31.👆 The user taps the button 5 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    };     (a) ON (b) OFF
  32. 32.👆 Code that runs when an event happens is called a ___. (a) headline (b) header (c) handler (d) hashtag
  33. 33.👆 The user taps the button 5 times. What number does the label show now?
    let points = 10;
    button.onTap = function () {
      points = points + 4;
      label.text = points;
    };
  34. 34.👆 A tap handler runs how many times if the user taps 4 times? (a) 4 (b) 0 (c) 8 (d) 1
  35. 35.True or false: a finger hits Like is a tap event. (a) False (b) True
  36. 36.True or false: the screen first opens is a timer event. (a) True (b) False
  37. 37.👆 What kind of event is this: a countdown hits zero? (a) a load event (b) a text event (c) a tap event (d) a timer event
  38. 38.👆 The user taps the button 1 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  39. 39.True or false: a countdown hits zero is a tap event. (a) False (b) True
  40. 40.👆 The user taps the button 7 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };

Answer key

  1. 17
  2. a timer event
  3. False
  4. True
  5. an action
  6. something that happens
  7. 24
  8. 3
  9. a timer event
  10. a load event
  11. OFF
  12. Hi, Riya!
  13. a tap event
  14. the user taps a button
  15. ON
  16. Hello, Kabir!
  17. Hello, Zoya!
  18. a tap event
  19. 23
  20. Hi, Kabir!
  21. 19
  22. 27
  23. False
  24. True
  25. Well done, Aman!
  26. False
  27. a text event
  28. 4
  29. Hello, Aman!
  30. 4
  31. ON
  32. handler
  33. 30
  34. 4
  35. True
  36. False
  37. a timer event
  38. 1
  39. False
  40. 3

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